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Some immigrants and refugees in Ontario at higher risk of psychotic disorders

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Some refugees and immigrants have a higher risk of psychotic disorders, with immigrants from the Caribbean and refugees from East Africa and South Asia at 1.5 to 2 times greater risk than the general population, according to a large study in CMAJ (Canadian Medical Association Journal).

"Given that Canada is currently experiencing a rapid growth in the population of foreign-born citizens - one of the highest rates of any Western nation - the mental health status of immigrants and refugees should be a national priority," writes Dr. Kelly Anderson, an assistant professor at Western University, London, Ontario, and a fellow at the Institute for Clinical Evaluative Sciences (ICES), with coauthors.

Canada receives approximately 250 000 immigrants and refugees each year. Ontario is home to the largest number of migrants in the country, who make up about 30% of the provincial population.

To determine whether first-generation immigrants and refugees to Canada were at higher risk of schizophrenia or schizoaffective disorder, researchers looked at health administrative data for 4 284 694 Ontario residents aged 14-40 years as of Apr. 1, 1999. They followed people over a 10-year period for a first diagnosis of psychotic disorder. Of the total study population, almost 10% of people (418 433) were migrants born outside Canada, and almost 23% (95 148) of migrants were refugees.

The incidence of psychotic disorders was 55.6 per 100 000 person-years in the general population, 51.7 among immigrants and 72.8 among refugees. Some immigrant groups (from Northern and Southern Europe and East Asia, for example) had lower rates than the general population. However, immigrants from the Caribbean and Bermuda had higher rates of schizophrenia, as did refugees from East Africa and South Asia.

"The differential rates cannot be explained by variations in the country of origin, and the selective migration of people who have an increased risk is increasingly being refuted as a plausible explanation," write the authors. "The pattern we observed in Ontario suggests that psychosocial factors associated with the migratory experience and integration into Canada may contribute to the risk of psychotic disorders."

The authors postulate that experiences of discrimination and racism may explain the higher rates of psychotic disorders in some immigrant groups, as indicated by previously published studies. Refugees may be more susceptible for several reasons, including earlier trauma in their home countries as well as obstacles in finding housing, jobs or health care when settling in Canada.

"Migrant status, in particular refugee status, needs to be considered as an important risk factor for psychotic disorders in Ontario," they conclude.

In a related commentary, Dr. James Kirkbride, University College London, London, United Kingdom, notes that this study provides important data on the immigrant experience to Canada; most literature focuses on Europe. Migrants to European countries have a higher risk of schizophrenia, with incidence in the black Caribbean population almost 5 times that of the general population.

"Perhaps the most striking finding from the study is that rates of psychosis were not elevated consistently among nonrefugee first-generation migrants relative to the general population," writes Dr. Kirkbride.

He suggests that the lower excess risk among migrants may be because Canada's ethnically diverse general population, against whom immigrants were compared, may also include some groups that tend to experience higher rates of schizophrenia.